The present invention relates to a control apparatus for a machine tool and a machining system comprising the control apparatus and a machine tool wherein, by supplying a raw workpiece and inputting data regarding a machining profile of a final product (hereinafter referred to as machining profile data), the workpiece to be machined is machined according to the machining profile data so that a final product can be fabricated.
In the conventional method of machining a workpiece by a NC machine tool, the first step is to prepare a drawing representing the profile of a product to be machined. A programmer determines the machining steps from the drawing and creates a NC program manually or by an automatic programming unit. An operator inputs the NC program into the NC machine tool while, at the same time, setting up the workpiece on the NC machine tool manually or by using an automatic workpiece changer. Then, the cutting tool to be used is preset, and the amount of tool offset is defined. The cutting tool is then mounted in the tool magazine of the NC machine tool. After that, the NC program is executed thereby to machine the workpiece and fabricate a product. Various inventions have hitherto been developed with the aim of automating these steps as far as possible and reflecting the knowhow accumulated by programmers and operators on the machining steps.
First to be cited is an automatic programming system disclosed in Japanese Unexamined Patent Publication (Kokai) No. 4-315550. This system comprises profile recognition means for extracting a machining profile from the data representing the machining profile of a workpiece, a machining conditions memory for storing optimum machining conditions, and automatic machining conditions setting means for automatically setting optimum machining conditions stored in the machining conditions memory. As a result, machining conditions can be set automatically without the manual operation of setting the machining conditions by the operator, thus eliminating the human errors which often accompany manual operation and making a superior machining operation possible. Further, the load on the operator and the time required for the operator to tend to the machine are reduced.
A second conventional machining system is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 4-138504. In this system, data on a workpiece including the material, surface roughness and the dimensional accuracy are stored beforehand and machining conditions are determined by a first neural network. The machining conditions can be corrected by the operator. This system further comprises learning means which, after an actual machining operation, corrects the machining conditions based on the machining result to produce corrected machining conditions while at the same time correcting the weight of the first neural network. The system furthermore comprises adaptive control means including a sensor for detecting the sparks, sound and the force generated during the machining process, and a second neural network supplied with the data from the sensor as temporal data in which the data is averaged with a predetermined time margin to detect the machining conditions at the moment thereby to correct the machining conditions dynamically. Even without a skilled operator, therefore, the workpiece can be machined under optimum machining conditions.
A third conventional technique concerns a method using the numerical control disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-26811. According to this method, a machining process and a machine tool are optimally selected in accordance with simplified input databased on the registration of various information files, the input of machining pattern data, the processing of a finish pattern, pattern recognition and the determination of the machining process. In this way, a machining area and machining steps high in production efficiency are selected, and tools, machining conditions and a tool path most suitable for the input patterns are determined. Both the production efficiency and the machining accuracy are improved further by post-machining measurement and correction.
Techniques are well known for automatically creating a tool path from the profile data of a product to be machined. An NC program can be automatically prepared by adding various machining conditions to the profile data. According to the first prior art described above, machining conditions are selected from a database in accordance with a predetermined algorithm based on the profile data of the product to be machined. These machining conditions can be considered static ones. In contrast, the second prior art is such that machining conditions which undergo a constant change are detected by a sensor, and the machining conditions set based on the detection result are adoptively controlled using the learning function of a neural network, so that dynamic machining conditions are determined in accordance with ever-changing machining requirements. The first and second prior art emphasize the automatic determination of machining conditions.
In the third conventional method, the operator inputs data, and machining conditions are automatically determined using a technique similar to the first and second prior art. In addition, automatic determination of a cutting tool and a tool path combined with a technique of measurement and correction after machining to finish an intended product without human labor.
These conventional techniques are based on the architecture of securing a high accuracy and a high production efficiency by feedback correction of the machining conditions, but not intended to realize a high-accuracy, high-efficiency machining process by predicting machining requirements and determining a tool path and machining conditions based on the prediction.
An object of the present invention is to provide a machine tool control apparatus and a machining system including the control apparatus and a machine tool, in which an intended product can be automatically machined at high efficiency while meeting the precision requirements in response to only profile data on the product to be finished and data on the workpiece to be machined.
Another object of the invention is to provide a machine tool control apparatus and a machining system including the control apparatus and a machine tool, in which machining requirements are predicted and a tool path and machining conditions are determined automatically in conformance with the predicted machining requirements, thus making possible a high-precision, high-speed machining process.
According to a first aspect of the invention, there is provided a machine tool control apparatus supplied with machining profile data for machining a workpiece, comprising input means for inputting workpiece data including machining profile data on a final workpiece profile and the material and the profile of the workpiece to be machined, data storage means for storing at least a selected one of machine data representing the specifications of the machine tool used for machining the workpiece and tool data representing the specifications of the tools held in the machine tool, and tool path determining means for generating a tool path for machining the workpiece and determining the conditions for machining the workpiece such as the rotational speed of the main spindle and the feed rate of the machine tool based on the data stored in the data storage means.
According to another aspect of the invention, there is provided a machining system supplied with the machining profile data for machining a workpiece, comprising: a machine tool for machining the workpiece; input means for inputting the machining profile data on the final profile of the workpiece and the material and profile of the workpiece to be machined; data storage means for storing at least a selected one of the machine data representing the specifications of the machine tool for machining the workpiece and the tool data representing the specifications of the tools held in the machine tool; predictive calculation means for predicting at least a machining load or interference between a tool and the workpiece based on the data input from the input means and the data stored in the data storage means; machining process determining means for selecting a tool and a machining pattern and determining a machining process based on the data input from the input means and the data stored in the data storage means; tool path determining means for generating a tool path for machining the workpiece and determining the conditions for machining the workpiece including the rotational speed of the main spindle and the feed rate of the machine tool based on the tool, the machining pattern and the machining process selected and determined by the machining process determining means, the result of predictive calculation made by the predictive calculation means, the data input by the input means and the data stored in the data storage means; and numerical control means for controlling the operation of the machine tool according to the tool path and the machining conditions generated and determined by the tool path determining means.